Forty years after succumbing to a mouth-watering marshmallow as a child, middle-aged adults still have a hard time resisting temptation, a new study finds. The results, published online August 29 in the Proceedings of the National Academy of Sciences, suggest that willpower is stable over a person’s lifetime.

“I’m impressed,” says psychologist and neuroscientist Bernd Figner of Columbia University, who wasn’t involved in the experiments. “It really is a unique study.”